The present invention relates to the field of thermal inkjet printing. More particularly, the present invention relates to the field of regulating temperature in a thermal inkjet print head.
Inkjet printers work by spraying ink at a sheet of paper or other print medium to create images or text. Inkjet printers are capable of producing high quality print approaching that produced by laser printers. Inkjet printers are generally less expensive than laser printers, but can also be considerably slower.
To produce words or pictures contained in data received by a printer from a host computer or network, the inkjet printer squirts drops of ink through extremely tiny nozzles. Bundled together, the hundreds of nozzles form a print head, which travels across the paper printing a horizontal line of the image. The nozzles fire many times per second. After completing a line, the paper is advanced and the next strip of the image is printed. This continues until the page is complete.
Inkjet printers can also print in color by squirting colored inks onto the paper. Most inkjet printers use four hues of ink in the well-established color set used on color printing presses, i.e., cyan, magenta, yellow, and black, often abbreviated as CMYK.
There are two basic types of inkjet printers: thermal and piezo. Most inkjet printers use thermal inkjet technology, which heats the ink to create a bubble that forces a drop of ink out of the nozzle. Tiny resistors may be used to rapidly heat a thin layer of liquid ink causing the bubble to form. As the nozzle cools and the bubble collapses, it creates a vacuum that draws more ink from a cartridge to replace the ink that was ejected. This process is repeated thousands of times per second. The time required to heat and then cool the nozzle theoretically slows printing speeds.
In contrast, piezoelectric inkjet printing, commonly referred to simply as piezo, pumps ink through nozzles using pressure. The print head regulates the ink by means of an electrical current passed through a material that swells in response to the electrical current to force ink onto the paper. Piezo print heads require vacuum pumps and large ink-absorbent pads to keep nozzles printing reliably. Piezo mechanical stability is also highly sensitive to small air bubbles, and the system may also need flushing with ink to purge trapped air, a process that wastes ink.
The present invention relates to thermal inkjet printing. Thermal inkjet performance can vary widely due to the temperature of the ink firing chamber and the ejected ink. Controlling temperature in a thermal inkjet printer is important in order to guarantee consistently good image print quality. This is due to changes in the physical characteristics of the ink, the nucleation dynamics of the ink and the refill characteristics of a thermal inkjet print head, all of which can vary with temperature. The print head temperature can vary due to ambient temperature, servicing (spitting) and the amount of printing being done with the print head.
Heating the print head before the start of the printing swath has been attempted to control temperature. This method has the disadvantage of having to predict the required temperature and adjust the delivered heat at the start of the printing zone to compensate for all possible changes of temperature during the printing swath. Temperature variations can be significant and very difficult to predict.
In one embodiment, the present invention may be described as a thermal inkjet print head with a temperature regulation system. The print head preferably includes a thermal inkjet print head and an array of Peltier devices in proximity to the thermal inkjet print head such that the array of Peltier devices can raise or lower the temperature of the thermal inkjet print head or components thereof.
In another possible embodiment, the present invention may be described as a thermal inkjet printing device with a temperature regulation system for a print head of that printing device. The printing device preferably includes a thermal inkjet print head and an array of Peltier devices in proximity to the thermal inkjet print head such that the array of Peltier devices can raise or lower a temperature of the thermal inkjet print head or components thereof.
The present invention also encompasses a method of regulating the temperature of a thermal inkjet print head by selectively heating or cooling the inkjet print head or components thereof with an array of Peltier devices.
The present invention also encompasses a method of making a thermal inkjet print head by forming a thermal inkjet print head, and forming an array of Peltier devices in proximity to the print head for regulating an operating temperature of the print head.